[clang-tools-extra] [clang-apply-replacements] Apply format only if --format is specified (PR #70801)

[Malcolm Parsons via cfe-commits]

pepsiman wrote:

`createReplacementsForHeaders()` is applying a cleanup without checking the `Cleanup` flag.
But clang-apply-replacements always sets `Cleanup` to `true` anyway.
The change looks good to me, but it might be working around a bug elsewhere.

https://github.com/llvm/llvm-project/pull/70801